High voltage transistors are often used as a switch, where the transistor has a high resistance that essentially blocks current in the “off” mode and a lower resistance that allows current in the “on” mode. The transistor has some resistance in the “on” mode, sometimes referred to as the resistance from drain to source in the “on” mode (Rdson.) The lower the Rdson, the less voltage drop across the transistor and more efficient the operation of the transistor. Higher Rdson values typically result in higher energy losses during switching from the “on” to the “off” mode, or vice versa, as compared to transistors with lower Rdson values.
A typical transistor in an integrated circuit includes a gate electrode as a control electrode overlying a channel of a semiconductor substrate. Spaced-apart source and drain regions are on opposite sides of the channel, and current can flow between the source and drain within the channel. A gate insulator is disposed between the gate electrode and the channel of the semiconductor substrate to electrically isolate the gate electrode from the substrate. A control voltage applied to the gate electrode controls the flow of current through the channel between the source and drain regions, where the control voltage can be used to turn the transistor on or off when used as a switch. A high voltage transistor may increase the distance between the drain and the gate, where a drain distance is the distance between the drain and the gate. Longer drain distances typically produce higher the current capacities due to lower substrate current for a high voltage transistor (compared to shorter drain distances with the same dopant level and design), but longer drain distances also tend to increase the Rdson. The resistance between the gate and the drain (sometimes referred to as the “drift” region) is typically higher than the resistance between the source and the drain for a high voltage transistor, so the resistance in the drift region is the major contributor to the Rdson. Reducing the drain distance or increasing the dopant level in the drift region can reduce the resistance in the drift region, but this also reduces the breakdown voltage of the high voltage transistor, which reduces reliability.
Accordingly, it is desirable to provide integrated circuits with high voltage transistors that have decreased Rdson values with comparable or superior reliability as compared to traditional high voltage transistors, and methods of producing the same. In addition, it is desirable to provide integrated circuits with high voltage transistors that are capable of transferring high currents without damage and with reduced voltage drop as compared to traditional high voltage transistors, and methods of producing the same. Furthermore, other desirable features and characteristics of the present embodiment will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.